welcome to Opti-World! Applying Opti-Coat Pro+ over Gloss-Coat would require some prep/polishing. The components that add gloss and slickness to Gloss-Coat will not allow a good bond with OCP+. A light polish and decontamination wash should suffice.
You can apply Opti-Coat Pro over Gloss-Coat, but need to remove the Opti-Seal first. A good decontamination wash will work - Power Clean or Paint Prep. IPA is a less reliable option. None of these cleaners will remove either Coating.
I've never heard of someone coating floor mats but I don't think there would be any issues. I'd agree with A&J/Guz that it's an expensive and somewhat short range solution. Something like Protection Plus would seem a better choice.
Different installers recommend different wait times, but my standard suggestions are -
All Coatings may be topped 1 hour after application
In either order - OCW and OS are fine immediately
Opti-Seal - layering I've seen anywhere from 1 hour to 24 hours, not sure about Instant Detailer but would think anywhere after 1 hour.
So I have the answer(s) from Dr G & Yvan:
Dr G: The white pads work better on some paints and specially in hot climates since they are not affected by heat as much as the orange pads. We will update the website information so that it differentiates the two better.
Yvan: The white pad is a strange animal , Iron fist in a a velvet glove if you
will. With Hyper Compound it cuts more then the Orange pad. On softer
paints it will finish better then even our black pad. This is why the
description has it as both a cutting and polishing pad. The cell structure
is different then our other waffle pads.